Porosity or other-type small leaks in metallic vessels (castings) usually intended to hold fluids under high positive or negative pressure, are a serious economic problem in the metal-vessel (especially casting) art. Attempts to seal such leaks by electric or flame welding have proven generally unsatisfactory, especially if the vessel is an aluminum-alloy casting because the worked-on areas would be made rough and discolored by the attempted repair. It is accordingly the principal object of this invention to provide a metallic-vessel-leak-repair method that economically produces a structurally sound repair job and which leaves the repair area unblemished. Other objects and advantages will become apparent as the following description proceeds.